Bionic Movements: Connecting Mind and Machine

When you lose the use of a limb, even the simplest of daily tasks can turn into a challenge. High-tech devices can help restore independence. New technologies are even making it possible to connect the mind to an artificial limb. These artificial limbs are called bionic prosthetic devices.

“To get back some of that lost function, you need some sort of assistive tool or technology to either enhance recovery or restore the capability of the anatomy that’s missing now,” says Dr. Nick Langhals, who oversees NIH-supported prosthetic engineering research.

This fast-moving research aims to improve people’s lives by restoring both movement and feeling.

Prosthetic Control

Traditional prosthetic devices use a body-powered harness to control a hand device. These are easy to use. With a shrug of your shoulder, the prosthetic hand or hook opens. With the release of your shoulder, the prosthesis closes. Through the feel of the cable tension across your shoulders, you know whether the prosthesis is open or closed without looking at it.

Newer, motorized hands are not as easy to learn how to use. To close the device, you contract the remaining muscles in your arm. An electrical sensor placed over those muscles detects the contraction and tells the hand to close. Since the original muscles that controlled the hand are gone, the remaining muscles must be retrained. Learning how to open and close a prosthetic hand in this way takes some time. And you still need to watch the device to know what it’s doing.

To make motorized hands more intuitive to use, researchers are developing ways to detect the electrical signals in your brain and nerves to help control advanced bionic prosthetics. This can be done many ways, such as by implanting tiny sensors in the parts of the brain that control movement or by attaching small electrodes to the amputated nerves. Either way, the patients simply think about moving their hand and computers translate it into the movements of a bionic prosthetic hand.

Two-Way Communication

To regain a sense of wholeness, a person with a bionic limb needs to do more than control the device. They also need to “feel” what it’s doing. New bionic devices can send sensation from the device back to the brain. This allows a person with a bionic device to feel like they are using their own limb.

“The most important thing about the research that we’re doing is this sense of wholeness,” says Dr. Paul Marasco, a biomedical engineering researcher at Cleveland Clinic.

One way to help a person feel their prosthetic hand is to move the remaining sensory nerves from the amputated hand to the skin of the upper arm. You can then use small robots to press on the skin of the upper arm when the hand is touching something.